Improvement in rasps



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WILLIAM rr. NICHOLSON, OE PROVIDENCE, RHODE ISLAND, ASSIGNOE To 'iHE NIOH- OLSON FILE COMPANY, or SAME PLACE.

Leners Peten: Ne. 94,503, elated september 7, '1869.

IMPROVEMENT IN RASPS.

The Schedule'efverred to in these Letters Patent and making part of the lama To all whom tt may concern.-

Be it known that I, WILLIAM T. NICHOLSON, of

lthe vcity and county of Providence, in the State of Rhode Island, have invented a' new and useful Improvement'in Files; and I do hereby declare that the following specification, taken in connection with the drawings, making a part of the same, is a full, clear, and exact description thereof.

Figure 1 is face view of the ordinary rasp-teeth.

Figure 2 is a face view of the rasp, with my irnlproved'teeth.' v

Figures 3 and 4 are face and sectional views of the teeth, enlarged.

v The purpose of my invention is to so form the teeth of a rasp that each ofthe several teeth shall be able to eiiect a shearingout upon the metal or material to which the ras'p is applied, and I accomplish this by making the cutting-edge of each individual tooth curved, or practically so, in two directions in relationto the surface ofthe file, the portion of the metal raised by the chisel being convex on its'outer and inclined surface, and presenting a cutting-edge either convex or concavev in relation to a Straight line sup.

posed to be drawn immediately in front of the tooth, and at right angles to its axis of elevation.

' The formation of the teeth, as shown in fig. 1 and fig. 2, respectively, will illustrate the difference be'- tweeu the common tooth and that which is my improvement.

In the former figure, representing the common teeth of rasps, the cutting-edge of each tooth is raised by a' ,punch,wl1ose cross-section is a plain triangle,` and,

consequently, the cnttingfedge of the tooth will be in a straight line.

In iig. 2, the cross-section of the punch, which is required to form the teeth is a mixtilinear triangle, the curved side of which forms the tooths cutting-edge. In the instance shown in the drawing, the several teeth a, figs. 2 and 3, require a punch whose edgeforming face isy convex, while to form the tooth b, Iig. 4, the corresponding face of the punch should be concave. In 'both cases the tooth raised by such punches will be capable of making a shearing-cut. It is-not necessary, however, that the outline of the cross-seetion of the cutting-face of the teethshould bea curved line; it may be 'composed of several straight lines, constituting the elements of a curved line.

Teeth formed as described can obviously beairanged to stand in any of the usual or preferred lines, across the face of the rasp, with the saine facility as if made in the common form.

. I am aware that a rasp has, before my invention, been made, with the arrangement of the cuttingedges of some ofthe teeth inclined to the longitudinal axis of' the rasp, while the remainder ofthe teeth are arranged in the common way, the eifect ot' which arrangement is to accomplish a partial shearing-eut.

My invention is independent of any means to obtaina result obtained from any peculiarityof arrangcment of the several rows of teeth, but resides in the peculiar character which each tooth individually possesses, and which enables it, without gard to its arrangement with respect to any other tooth in the rasp,

to produce a shearing-cut.

What I claim as my invention, and desi-re to secure by Letters Patent, is

The improvement in, rasps, which consists in making the cutting-edges of the several teeth thereof in the form and of the character substantially as herein described, for the purpose of enabling `each of such teeth to exert a shearing-cut, when applied to use as set forth.

W. T. NICHOLSON. Witnesses:

BENJ. F. THURSTON, PETER F. HUGHES. 

